Pimple behind the upper lip, help?

i don't know how i got it, but i just noticed it now. it looks like a pimple, its really small and no there isn't a white-ish tint inside of it. if i run my tongue over it it feels like a little ball. its located behind my upper lip, to the left. i recently had a root canal, not successful cuz my roots are very small and the dentist couldn't go through with the last two roots. he warn me if i saw any pimples/blisters near the tooth to come in and get it checked out, but the pimple like bump is on the opposite side, and its not on the gums. if any of you know what it is please tell me, and if i need to get it checked out, even though that might be a problem atm b/c my dad is on vaca and mom is working during dentist hours.